The present disclosure relates to a unit retraction device for retracting into an apparatus body a unit that is extractably and insertably loaded in the apparatus body, and to an image forming apparatus, such as a copier, printer, or facsimile machine, provided with such a unit retraction device.
Conventionally, an image forming apparatus such as a copier, printer, or facsimile machine is, in a bottom part of its apparatus body, provided with a paper feed cassette for accommodating a plurality of sheets of paper (recording medium) in such a way that the paper feed cassette is extractable out of the apparatus body. By a feeding means, comprising a pickup roller or the like, arranged over the paper feed cassette and by a separating/transporting means, comprising a paper feed roller pair or the like, the paper accommodated in the paper feed cassette is fed out one sheet after another so as to be transported to an image formation section and on to a fusing device, so that an image is formed on the paper.
In an image forming apparatus as mentioned above, the paper feed cassette is loaded into and unloaded out of the apparatus body manually by a user on occasions of paper replenishment and paper size change. On such occasions, the paper feed cassette may not be completely inserted into a predetermined position (loaded position) inside the apparatus body. In that case, the paper feed cassette is positioned improperly, leading to an image being formed off the center of the paper in its width direction, or to transport failure.
Moreover, the paper feed cassette along with the paper accommodated in it may turn out to be so heavy that the user finds difficulty inserting the paper feed cassette into the loaded position. For easier handling of the paper feed cassette, there have been proposed various retraction devices for retracting the paper feed cassette into the loaded position inside the apparatus body.
For example, in one known retraction device, when the paper feed cassette has been loaded up to a predetermined position, engagement by an engaging portion of the retraction device is released so that a retraction force is discontinued. In another known retraction device, a force storing means is provided which, after engaging with a sheet accommodating means, gradually stores a retraction force as the sheet accommodating means moves in the loading direction, wherein retraction into the loaded position is achieved by releasing the retraction force in the force storing means before or after the retraction force by a retracting means becomes maximal.
A known image forming apparatus is provided with a retraction force generating means comprising a plurality of biasing members which generate biasing forces in different biasing directions and a plurality of rotary members for generating a retraction force from the biasing forces of those biasing members. Yet another retraction device is provided with a restricting member which suppresses increase in retraction speed by generating a load commensurate with the retraction speed with which a paper feed tray is retracted. This retraction device can suppress increase in the retraction speed of the paper feed tray, and can thereby suppress impact during loading of the paper feed tray.